Effects Of Drought Stress On Resistance Physiological And Biochemical Indexes Of Taraxacum Mongolicum Hand-Mazz

Dandelion is also known as huang hua di ding,po po ding,hua hua lang,which belongs to Compositae,taraxacum,perennial herb.It is called one of the“Eight King Kong”in the Chinese medicine industry and rich in various nutrients elements,trace elements,and a lot of minerals such as iron and calcium necessary for the human body.With the improvement of people's living standards year by year,the concept of health begins to be deeply rooted in the hearts of the people.People's choice of food firstly includes green and health as the primary factors.In recent years,domestic dandelion edible and medicinal-related industries have developed quickly,but the research more focused on nutrients and active substances in the dandelion,and there are few studies on planting and cultivation.In order to enrich the theory of dandelion cultivation management technology,the study chose a kind of commercially available dandelion as the research object,setting control?CK?,moderate stress treatment?MST?,severe stress treatment?SST?,moderate stress treatment rewatering?MST+RW?and severe stress treatment rewatering?SST+RW?.The related physiological indexes such as shoot and root accumulation,chlorophyll fluorescence parameters,chlorophyll content,root activity,leaf protective enzyme activity and osmotic substance content of dandelion under different treatments were determined.The main research results are as follows:1.Under drought stress treatment,the growth of shoot and root were inhibited.The shoot accumulation of MST and SST were significantly lower than the CK.With the prolongation of time,the overall performance showed a downward trend,but the root-shoot ratio showed an increasing trend and the SST increased.The amplitude was greater than MST,and the root-shoot ratio reached the maximum at 15 d after drought stress.Rewatering treatment could improve the inhibition of dandelion under stress treatment.After 5 days of rewatering,the dandelion was restored to normal growth level with moderate and severe stress treatment.The MST showed a better recovery ability than the SST in the exprement time.At 5 d and 10 d,the recovery ability of SST was stronger than the MST.2.The root activity of dandelion,with the prolongation of drought time,MST and SST showed a downward trend,and the root activity was CK>MST>SST.Rewatering significantly increased the root activity of MST and SST,and the root activity SST₅+RW>MST₅+RW>CK.SST₁₀+RW and MST₁₀+RW were not significantly different rewatering after 5 days of drought,as the same as SST₁₅+RW₅ and MST₁₅+RW.3.Drought stress treatment could enhance the activity of protective enzymes?SOD,POD,CAT?in leaves of dandelion.The enzyme activity were SST>MST>CK.Rewatering could effectively reduce the activity of 3 protective enzymes in dandelion leaves,such as POD activity,MST₁₅+RW and MST₅+RW were recovered to the level of control enzyme activity;CAT activity,only MST₅+RW could be restored to the control level;SOD could not be reduced to the level of treatment with the control.4.Under drought stress treatment,the contents of 3 osmotic adjustment substances?proline,soluble sugar,soluble protein?in leaves of dandelion showed different trends.The content of proline and soluble sugar increased in MST and SST,while the content of soluble protein showed an upward trend in MST,but first increase and then the downward trend in SST.The contents of proline,soluble sugar and soluble protein were SST>MST>CK.After rewatering,the contents of 3 osmotic adjustment substances were reduced.Proline was restored to the control level under MST₅+RW,MST₁₀+RW,SST₅+RW;soluble sugar content was reduced to the level of the control group under MST₅+RW and SST₅+RW;soluble protein was less affected by rehydration,and the drought stress treatment could not be restored to the control level.5.The drought stress treatment could reduce the content of chlorophyll a.The MST and SST were lower than the control.The drought stress was carried out for 10 days.There were no significant differences between MST and SST.The other time MST was significantly lower than SST.Rehydration could restore the content of chlorophyll a to the control level under MST₅+RW.The content of chlorophyll b was stable between the treatment groups,and there were no significant differences between MST and control,while SST was significantly lower than control under MST after 10 days.Rewatering showed minor effects on the increase content of chlorophyll b under SST.The trend of total chlorophyll and chlorophyll a was consistent.6.Drought stress treatment could effectively reduce the chlorophyll fluorescence parameters of dandelion including Fv/Fm?Fv'/Fm'?PS?and qP.With the prolongation of drought stress,the overall performance showed a downward trend,and the decrease of chlorophyll fluorescence parameters was positively correlated with the degree of drought stress.Rewatering showed a higher recovery effect on the early stage of drought stress and could be restored to the same level as the control.